A recent video printer forms an image by using an ink ribbon produced by dissolving a disperse dye into a hydrophobic high polymer and thermally transferring the dye contained in the ink ribbon onto a receptor layer applied on a transfer target material, such as synthetic paper, in accordance with image signals.
The disperse dye is employed herein for the following reason. Since the disperse dye is hydrophobic, it exhibits satisfactory dyeing property on the transfer target material and hence practical sensitivity on transfer.
However, when the disperse dye is used as the dye for the ink ribbon, it is difficult to assure fixation after printing.
Meanwhile, a basic dye, or a so-called cationic dye, having high visibility and coloring property peculiar to the basic material is known as a dye for dyeing acrylic fibers. It is proposed to use the cationic dye as a dye for the ink ribbon is proposed, as disclosed in the U.S. Pat. No. 4,664,671.
The cationic dye is known to exhibit excellent light fastness and wet coloring fastness on the acrylic substrate. However, since the cationic dye has hydrophilic property, it is difficult to disperse the cationic dye uniformly and stably into the hydrophobic high polymer, such as butyral resin, which is broadly used as a binder for the ink ribbon. In addition, there is no measure to fix the image in or after image formation.
To solve such problems, the present Applicant has proposed a technique of using a hydrophobic cationic dye for the ink ribbon while using an interlayer compound ion-exchangeable with the cationic dye and dissolved into a binder high polymer for the receptor layer of the printing paper, and then holding and fixing in the interlayer compound the cationic dye transferred into the receptor layer, in the JP Patent Kokai Publication No. 4-299183.
With this technique, however, it is necessary to make the cationic dye hydrophobic in advance by ion exchange using an organic anionic surface active agent. Thus, the production process of the ink composition and the ink ribbon is complex.